Each year there is a ScavOlympics, which is an excuse for further ridiculous contests, and a road trip where (sub-)teams might have to drive almost a thousand miles just to solve a clue. Team members have got permanent tattoos, circumcisions and even marriages in order to score Scavenger Hunt points. (Well, the latter two have only happened once each.) Famous successfully-completed items include a real live breathing elephant and a working, though very small, nuclear breeder reactor, which created about enough U and Pu to mildly concern a microbe. For further information and reminiscence, see a Slashdot article and a judge's weblog.
Naturally, I am highly jealous, and this looks set to go on the theoretical list of the world's great unique games which the true game raconteur ought to try at least once. Except it might not be so unique after all. (The Oxford University Invariant Society's hunt doesn't even slightly compare, not even when addedentry and I were running it. There's no reason why it couldn't compare, with sufficient scope, scale and wide participation, because most maths geeks really are sufficiently freaky to do anything stuntesque in the name of entertainment, but it generally takes them - us! - until they - we! - stop caring about mathematics to realise this.)
The Slashdot article has a reply from a French poster who suggests that many of their grandes écoles have similar hunts, and Wikipedia's general scavenger hunts page suggests that the University of Melbourne's hunt attempts to give lie to Chicago's "world's largest" claim by virtue of having more teams and a bigger list of items to find. The downside is that I cannot corroborate this claim at all - a search throughout unimelb.edu.au reveals very little. The student union calendar (bottom thereof) suggests it starts on Thursday, running overnight, but there's very little detail to it. There are sundry silly contests, but I think they are more to do with the "Prosh Week" rag-week antics at large rather than the hunt itself.
However, the University of Melbourne does have its own Puzzle Hunt, run by the rather rum-looking Mathematics and Statistics Society. (They also run the Maths Olympics - -ics rather than -iad - which is combination mathematical puzzle contest and lecture-hall-bound running race. I approve.) The 2005 hunt had a very interesting format and I'm a little disappointed that nobody has brought it to my attention already. There ought to be a weblog for these sorts of things...
Five puzzles are released at midday (local time) each day of a working week. On the Saturday, a meta-puzzle is released to tie the 25 answers together. Solving a puzzle on the day it's set is worth 4 points. 24 hours after a puzzle's release, a clue is given for the puzzle, but it drops from 4 points to 3; another 24 hours later, another clue but it's only worth two points; 72 hours after the start, a third clue and you can scrape it up for a single point. First team to solve the meta and retrieve the hidden MacGuffin wins AU$200, the two non-winning teams with the highest point scores at that point win small money.
Teams are limited to ten members, each with an e-mail address, but "...in particular members do not need to have an association with the University of Melbourne or reside in Australia. A team may use any source of information, including the internet and other people." That slightly devalues the ten-person limit to me, but there's a sportsmanship clause in there which (I guess) straightens things up. It's all Internet-based, and each team is limited to 100 guesses per day, which is wise. There's no reason why other universities couldn't do exactly the same thing; where is Oxbridge's own Puzzle Hunt, I wonder?
Anyway, the 2004 hunt was in September and the 2005 hunt in April, so I guess the 2006 hunt will be in about minus January - or, more likely, next April again. As they're making it so easy for overseas folks to take part, would there be interest in a general Team LiveJournal, to be assembled closer to the time?
In other news, Ravenchase organise treasure hunts and similar amazing races in Richmond, VA and Washington DC; I'm on a hunt of my own for the still-MIA sir_gareth. Please pick up the white phone.